This invention relates to photonic devices in general, and more particularly to tunable filters and tunable lasers.
Tunable Fabry-Perot filters and tunable vertical cavity surface emitting lasers (VCSEL""s) have recently generated considerable interest in the art. Among other things, these devices are believed to have application for a wide range of different optical components and systems, e.g., wavelength division multiplexing (WDM) fiberoptic systems, switches, routers, etc.
In some tunable Fabry-Perot filters and in some tunable VCSEL""s, tuning is achieved by using an electrostatic field to move a top mirror relative to a bottom mirror, whereby to change the length of the Fabry-Perot cavity and hence tune the wavelength of the device.
While such a construction is advantageous in that it provides a fast and easy way to tune the device, in practice it has proven difficult to produce relatively uniform devices. Significant performance variations typically occur from device-to-device and from batch-to-batch. In addition, significant performance variations can also occur with a specific device over time, as the device ages, changes temperature, etc.
As a result, one object of the present invention is to provide a novel wavelength locker for use in tuning a tunable Fabry-Perot filter and/or a tunable VSCEL to a precise, known wavelength.
Another object of the present invention is to provide a novel method for tuning a tunable Fabry-Perot filter and/or a tunable VSCEL to a precise, known wavelength.
Still another object of the present invention is to provide a novel optical system incorporating the aforementioned wavelength locker.
These and other objects are addressed by the present invention. In one form of the invention, there is provided apparatus for use in tuning a tunable optical device to a target wavelength, the apparatus comprising a beam splitter for tapping a portion of the light emerging from the tunable optical device; a walk-off reflector for dividing the portion of light from the beam splitter into a plurality of beams; a multiple etalon for tailoring the light from at least two of the plurality of beams provided by the walk-off reflector; a multiple detector for detecting light from the multiple etalon and the walk-off reflector, the multiple detector providing a plurality of output signals; and a control unit for controlling the tunable optical device by providing a control signal to the tunable optical device according to the output signals provided by the multiple detector.